s390/dasd: fix disconnected device with valid path mask

Path verification is either done via dasd_eckd_read_conf() which is
triggered during online processing and resume or via
do_path_verification_work() which is triggered after path events.
The dasd_eckd_read_conf() version added paths unconditionally and did
not check if the path mask was empty. This led to devices having the
disconnected stop flag set but a valid path mask. So they where not
working although they had paths validated successfully. After a resume
this state could even not be solved with additional paths added.

Fix by checking for an empty path mask in dasd_eckd_read_conf() and
clearing the device stop bits for a newly added channel path.
Reviewed-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NStefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd_eckd.c

@@ -1171,7 +1171,12 @@ static int dasd_eckd_read_conf(struct dasd_device *device)
 			path_data->ppm |= lpm;
 			break;
 		}
-		path_data->opm |= lpm;
+		if (!path_data->opm) {
+			path_data->opm = lpm;
+			dasd_generic_path_operational(device);
+		} else {
+			path_data->opm |= lpm;
+		}
 		/*
 		 * if the path is used
 		 * it should not be in one of the negative lists